1. Field of the Invention
The present invention relates generally to a self-diagnosis and repair system for an image forming apparatus, and more particularly, to a system capable of making self-diagnosis and self-repair of the operating state and the like of an image forming apparatus utilizing artificial intelligence and knowledge engineering which have been studied extensively in recent years.
2. Description of the Prior Art
In the development field of precision instruments, industrial machines and the like, expert systems utilizing artificial intelligence (so-called AI) techniques have been being studied extensively in recent years for the purpose of realizing labor saving in maintenance work and long-term automatic operation. The expert systems include one for making self-diagnosis to judge whether or not a fault is caused in an apparatus and making self-repair of the fault caused.
In a fault diagnosis system by the conventional expert system, such limitations have been pointed out that (a) there is no versatility in knowledge, which makes it impossible to make a fault diagnosis on a variety of objects, (b) a diagnosis cannot be made on unknown faults, (c) the quantity of knowledge required for fault diagnosis is increased explosively as an object becomes complicated, thus making implementation difficult, (d) it is difficult to acquire knowledge, and the like.
More specifically, in a conventional automatic control system and fault diagnosis system, an actuator corresponding to a sensor is basically made to operate on the basis of an output of the sensor. That is, a type of automatic control and fault diagnosis has been made by a predetermined combination of a sensor and an actuator. Accordingly, a certain sensor basically corresponds to a particular actuator, and the relationship therebetween has been stationary. Therefore, the conventional system has the following disadvantages:
(1) The relationship between parameters of the sensor and parameters of the actuator must be clearly expressed numerically.
(2) From the reason mentioned in the above item (1), the relationship between parameters of the sensor and parameters of the actuator depends largely on an objective machine. Accordingly, the conventional system is lacking in versatility, that is, cannot be utilized for a variety of objects.
(3) The relationships between parameters of respective sensors and between parameters of respective actuators have no relation with control. Consequently, only simple control based on the relationship between parameters of the sensors and parameters of the actuators which correspond to each other can be carried out.
More specifically, in the designing stage, faults which might occur must be forecast and mechanisms for countermeasures against the faults must be incorporated, and unknown faults cannot be handled.
(4) From the reason mentioned in the above item (3), secondary effects exerted on other actuators might be caused by the operation of an arbitrary actuator.
Thus, in the conventional automatic control system and fault diagnosis system, only a fault diagnosis based on sets respectively including independent sensors and actuators and fault repair based on the fault diagnosis have been made in such a manner that forecasting fault A is made on the basis of a set A of a sensor A and an actuator A, forecasting fault B is made on the basis of a set B of a sensor B and an actuator B, and forecasting fault C is made on the basis of a set C of a sensor C and an actuator C.